Multicasting is an important and challenging goal for heterogeneous wireless ad hoc networks, as it allows transmission and routing of packets to multiple destinations using fewer network resources. In mission-critical environments, the same information needs to reach multiple destinations with minimum delay and loss. This calls for formal and systematic techniques that can capture requirements adequately and implement them accurately, thereby providing the desired level of quality of service (QoS) for multicast communications. This paper provides a formal model for the heterogeneous wireless network and proposes a formal language that can specify and implement requirements, policies, instructions and abstractions for multicast communication over such networks. The language, named Multicast Specification and Implementation Language (MSIL), is also presented as a communication and control language for multicast configuration management, transmission, routing and QoS. The syntax and semantics of MSIL are described and discussed in detail. The applicability of MSIL constructs in modeling requirements for multicast network management is analyzed and demonstrated. Example MSIL programs, illustrating the expressiveness of the language, are developed for multicast QoS.